Transpiration as a Necessary Evil

The
stomata are primarily meant for absorption of CO2 but these also
help in exchange of gases, but at the same time water vapors also escape
through stomata. Thus transpiration is described as necessary evil because it
is an inevitable process but potentially harmful. Loss of water can lead to
wilting, serious desiccation, and often death of a plant, if there is shortage
of water. There is good evidence that even mild water stress results in reduced
growth rate, and reduction in yield.

However,
transpiration is beneficial to the plants in several ways.

1) Mineral Absorption: Minerals absorbed in water are
absorbed into the roots; move up through the plant in the transpiration stream.

2) Optimum Turgidity: In some plants if transpiration is
not allowed to occur, plants become very turgid, do not grow well and there
is shortage of water in their
cells.

3) Energy Exchange: When water is evaporated from the
exposed surface of cells of leaves, it exerts a cooling effect on plant.

4) Effect on Growth and
Development:
Transpiration is a necessary factor in the normal growth of some plants e.g.
pear, sunflower.

5) Absorption of Water: Water is conducted or transported in
upward direction in most tall plants due to transpiration.